The bug
If the sneak mode in control settings is set to "toggle", then players who die while sneaking will still be sneaking after they respawn. However, after respawning, sculk sensors will detect the movement of these players even though they are still sneaking.
Steps to reproduce
Ensure that your sneak mode in control settings is set to "Toggle" instead of "Hold".
Create a new peaceful superflat world.
Execute the following commands:
/gamerule doMobSpawning false
,/kill @e[type=!player]
and/gamemode survival
.Crouch.
Give yourself a sculk sensor and place it down.
Set the spawnpoint next to the sculk sensor.
Execute
/kill
. You should respawn crouching.Wait for the sculk sensor to stop clicking and move.
❌ The sculk sensor will pick up the vibrations.
Expected result
The sculk sensor should not detect the movement of crouching players, and they shouldn't emit vibrations, per MC-211243.
Linked issues
Attachments
Comments

Done.

I was able to reproduce (in 21w37a), but only if the sneak mode in control settings is set to "toggle". If it is set to "hold", then you're not crouching when you respawn, even if you continuously hold the shift key as you respawn. I will update the description accordingly.

Thanks, @unknown. Relates to MC-237042.

This is fixed in 1.20 Pre-release 6, the player no longer sneaks client-side after respawning.
I am unable to reproduce this issue in 1.17.1 Release Candidate 2. Could you provide some steps on how to go about reproducing this?